Satellite navigation systems, such as the global positioning system (GPS), enable a receiver to determine a location from ranging signals received from a plurality of satellites. The ranging signals can be broadcasted on frequencies, such as the L1 signal (1.57542 gigahertz [GHz]) and/or L2 signal (1.2276 GHz). L1 can have a wavelength of about 19 centimeters (cm) and L2 can have a wavelength of about 24 cm. Position can be determined from code and/or carrier phase information. A code division multiple access (CDMA) code is transmitted by the GPS satellites to the receiver and correlated with replica codes to determine ranges to different satellites. Accuracy can be enhanced using real-time kinematic (RTK) processing of carrier phase information. Accuracy at the level of tens of centimeters is possible with RTK carrier phase integer ambiguity resolution. RTK carrier phase integer ambiguity resolution can be used in applications with very accurate positional location information requirements and high integrity requirements.
High-accuracy relative positioning data with minimally acceptable integrity levels provided by RTK processing can be used in land surveying, precision agriculture, and/or construction applications. In other applications, such as those that present a substantial risk to human life, precision positioning with both high accuracy and high integrity is desirable. For example, applications that involve landing an aircraft, mid-air refueling, or coordinated formations flight can use a RTK positioning technique that is both highly accurate and also provides a high integrity level (e.g., high integrity protection level).
A high integrity protection level operates from the assumption that the GPS measurement data is without fault. In order to further increase the integrity of any real time kinetic positioning techniques, a positioning system may monitor the received data in order to minimize the effects of faulty measurements. Monitoring, however, may not remove the possibility of using faulty measurements to calculate GPS positions in some examples.
Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended.